Ballpoint pen refill

ABSTRACT

A ballpoint pen refill has an ink-accommodating tube ( 1 ) containing an ink ( 6 ) having a thixotropic property and a greaselike ink follower ( 7 ) capable of moving together with the ink ( 6 ) as the ink ( 6 ) is consumed so as to be contiguous with the rear end of the ink ( 6 ) to prevent the reverse flow of the ink ( 6 ). The ink-accommodating tube ( 1 ) has a small diameter portion ( 3 ) formed at a front side and a large diameter portion ( 2 ) having a diameter greater than the diameter of the small diameter portion ( 3 ) and extending rearward from the small diameter portion ( 3 ). A ballpoint pen tip ( 5 ) rotatably holding a ball ( 4 ) is inserted in the small diameter portion ( 3 ) of the ink-accommodating tube ( 1 ). A regulating member ( 1 5) has a column ( 15   a ) which is press-fitted in the small diameter portion ( 3 ). The column ( 15   a ) of the regulating member ( 15 ) has an inclined end surface ( 14 ) at its front end inclined at a predetermined angle to a plane perpendicular to the axis (O) of the ink-accommodating tube ( 1 ). The regulating member ( 15 ) is provided in its side surface ( 17 ) of the column ( 15   a ) with a fluid passage ( 18 ) extending rearward from the rear end of the inclined end surface ( 14 ) to enable the ink and air to flow therethrough in the ink-accommodating tube ( 1 ).

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a ballpoint pen refill having anink-accommodating tube containing an ink having a thixotropic propertyand a greaselike ink follower directly put in the ink-accommodating tubeso as to be in contact with the rear end of the ink to prevent thereverse flow of the ink and capable of advancing together with the rearend of the ink as the ink is consumed.

2. Description of Related Art

A ballpoint pen refill has an ink-accommodating tube containing an inkhaving a thixotropic property and a greaselike ink follower directly puttherein so as to be in contact with the rear end of the ink to preventthe reverse flow of the ink and capable of advancing together with therear end of the ink as the ink is consumed.

The ink having a thixotropic property is consumed at a consumption ratehigher than that at which the oil ink of the ballpoint pen is consumed.Generally, the ink-accommodating tube has a large diameter portioncontaining the ink and a small diameter portion holding a ballpoint pentip which rotatably holds a ball. Some ink-accommodating tubes are of atwo-section construction having a large diameter portion and a smalldiameter portion such as mentioned above, and other ink-accommodatingtubes are of a three-section construction having a big diameter portion,a small diameter portion and a medium diameter portion connecting thelarge diameter portion and the small diameter portion.

When such a ballpoint pen refill is impacted, the ink-accommodating tubeand the ink tend to slide relative to each other. Consequently, animpulsive force resulting from the weight of the ink acts on the inkfollower if the ballpoint pen tip is directed upward or the sameimpulsive force acts on the ball if the ballpoint pen tip is directeddownward.

When the impulsive force acts on the ink follower, the impulsive forcecan be absorbed by the viscosity of the ink follower and the physicalperformance of the ink-accommodating tube, such as the wettability ofthe inner surface of the ink-accommodating tube with the ink follower.

When the impulsive force acts on the ball, the impulsive force is borneonly by a front end edge of the ballpoint pen tip formed by spinning orthe like so as to hold the ball in the ballpoint pen tip. In a ballpointpen tip having a small ball, the wall thickness of the front end edge ofthe ballpoint pen tip holding the small ball is small and an exposedportion of the ball projecting from the front end edge is small and,therefore, the edge of the front end edge is liable to come into contactwith a paper sheet.

Consequently, the front end edge is worn and the ability of the frontend edge to hold the ball lessens as the ballpoint pen is used and,eventually, the ball falls off the front end edge when an impulsiveforce acts on the ball. The applicant of the present patent applicationhave previously proposed an improved ballpoint pen refill particularlyfor a retractable-type ballpoint pen which is carried around with itsballpoint pen tip directed downward, capable of eliminating thepossibility of falling of the ball off the front end edge in JapaneseLaid-Open Publication No.175078/1997. This previously proposed ballpointpen refill has an ink-accommodating tube provided with a ballpoint pentip in a front end portion thereof, and a partition wall disposed behindthe rear end surface of the ballpoint pen tip and provided with an inkpassage.

When fabricating a ballpoint pen refill including an ink-accommodatingtube containing an ink having a thixotropic property and a greaselikeink follower, air is entrapped in the ink when filling the ink and theink follower in the ink-accommodating tube. If air stays in theballpoint pen tip or the like, the ink is unable to flow through an inkpassage or the flow of the ink is obstructed, and the ink is unable torun properly. Therefore, air entrapped in the ballpoint pen refill mustbe discharged outside. In a stationary state, both the ink and the inkfollower are highly viscous, air entrapped in the ballpoint pen refillis unable to flow and to escape naturally from the ballpoint pen refilleven if the ballpoint pen refill is held with the ballpoint pen tipdirected downward.

Therefore, the ballpoint pen refill is mounted on the rotor of acentrifuge with the ballpoint pen tip directed radially outward and therotor of the centrifuge is rotated to force the ink toward the ballpointpen tip by centrifugal force so that air entrapped in the ballpoint penrefill is discharged outside forcibly through the open rear end of theink-accommodating tube.

In the ballpoint pen refill provided with the partition wall disposedbehind the ballpoint pen tip, air staying in a front end portion of theink-accommodating tube in front of the partition wall is stopped by thefront end surface of the partition wall when the ballpoint pen refill isturned on the centrifuge and air stays in the front end portion of theink-accommodating tube. It was found that the flow of air toward theopen rear end of the ink-accommodating tube is obstructed. Air cannot bedischarged outside through the open rear end of the ink-accommodatingtube. Air blocks the ink passage formed in the partition wall or an inkpassage formed in the ballpoint pen tip to cause the unsatisfactory flowof the ink.

The present invention, which has an ink-accommodating tube containing anink having a thixotropic property and a greaselike ink follower capableof moving together with the ink as the ink is consumed and of preventingthe reverse flow of the ink, has been made in view of theabove-mentioned problems. It is an object of the present invention toprovide a ballpoint pen refill which is formed in a structure that canprevent the action of an impulsive force on a ball resulting from theweight of the ink due to the movement of the ink and theink-accommodating tube relative to each other and that can prevent airwhich is entrapped in the ink when filling the ink and the ink followerin the ink-accommodating tube from staying in the ink-accommodating tubeduring a deaeration process for removing air entrapped in the ink fromthe ink-accommodating tube.

SUMMARY OF THE INVENTION

To achieve the object, the present invention provides a ballpoint penrefill which includes: an ink-accommodating tube containing an inkhaving a thixotropic property and a greaselike ink follower placedbehind the ink adapted to move as the ink is consumed and to prevent thereverse flow of the ink, and having a small diameter portion formed at afront side and a large diameter portion formed at a rear side with adiameter larger than a diameter of the small diameter portion; aballpoint pen tip inserted in a front end of the small diameter portionand rotatably holding a ball; and a regulating member having a columnpress-fitted in the small diameter portion. The regulating memberincludes an inclined end surface formed at a front end of the column andinclined at a predetermined angle to a plane perpendicular to an axis ofthe ink-accommodating tube, and a fluid passage extending rearward froma rear end of the inclined end surface along a side surface of thecolumn to enable the ink and air in the ink-accommodating tube to flowtherethrough.

Preferably, the predetermined angle is determined taking a magnitude ofa centrifugal force to be exerted in a direction parallel to the axis ofthe ink-accommodating tube on the ink in a deaerating process forremoving an air entrapped in the ink-accommodating tube and a viscosityof the filled in the ink-accommodating tube into consideration so thatthe air is not restrained from flowing by the inclined end surface inthe deaerating process.

Preferably, the regulating member has a main portion located behind thecolumn and having a diameter smaller than an inside diameter of theink-accommodating tube and greater than a diameter of the column, and atapered portion connecting the column and the main portion, the fluidpassage extends from the rear end of the inclined end surface throughthe side surface of the column beyond a rear end of the column.

Preferably, the tapered portion is inserted in the ink-accommodatingtube and is not in close contact with an inner surface of theink-accommodating tube, and the fluid passage extends to at least aportion of the tapered portion.

Preferably, the ink-accommodating tube has a shoulder portion forming atransitional portion between the small diameter portion and the largediameter portion. A recess is formed on an outside surface of theshoulder portion to enable air filling a barrel to flow rearward whenthe ink-accommodating tube is inserted in the barrel. A projection isformed on the inner surface of the ink-accommodating tube at a positioncorresponding to the recess, and the tapered portion comes into contactwith the projection so that a space is formed between the inner surfaceof the ink-accommodating tube and a surface of the tapered portion.

Preferably, the inclined end surface is formed as a flat surface.

Preferably, the inclined surface is formed as a convex conical surfaceprojecting from the front end of the column.

Preferably, a plurality of fluid passages extend rearward from a rearend of the convex conical surface.

Preferably, the fluid passages are arranged at equal angular intervalsabout the axis of the ink-accommodating tube.

Preferably, the ballpoint pen tip is provided with a spring pressing theball forward so as to press the ball closely against an inner surface ofa front end of the ballpoint pen tip.

Preferably, the small diameter portion has a thin section with a frontend in which the ballpoint pen tip is inserted, a medium section of adiameter greater than a diameter of the thin section and smaller thanthe diameter of the large diameter portion and connecting the thinsection and the large diameter portion, and the column of the regulatingmember is press-fitted in the medium section.

Preferably, an end plug provided with a vent hole allowing air passageis fitted in an open rear end of the ink-accommodating tube.

In the ballpoint pen refill of the present invention with the regulatingmember, the regulating member prevents the action of an impulsive forceresulting from the weight of the ink on the ball even if the ink and theink-accommodating tube are forced to move relative to each other by animpulsive force exerted on the ballpoint pen refill.

when air, which was entrapped in the ink having a thixotropic propertyand the greaselike ink follower in the process of filling the ink havinga thixotropic property and the ink follower in the ink-accommodatingtube, is discharged through the open rear end of the ink-accommodatingtube by applying centrifugal force on the ink on a centrifuge, the flowof air staying in a space in front of the regulating member is notobstructed by the regulating member, and air can surely be discharged.Therefore, air will not block the ink passage and hence the flow of theink is not obstructed by the entrapped air.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a ballpoint pen refill in afirst embodiment according to the present invention;

FIG. 2 is an enlarged end view taken on line I—I in FIG. 1;

FIG. 3 is a side elevation of a regulating member employed in amodification of the ballpoint pen refill shown in FIG. 1;

FIG. 4 is an enlarged end view taken on line II—II in FIG. 3;

FIG. 5 is a longitudinal sectional view of a ballpoint pen refill in asecond embodiment according to the present invention;

FIG. 6 is an enlarged end view taken on line III—III in FIG. 5;

FIG. 7 is an enlarged fragmentary longitudinal sectional view of aportion of the ballpoint pen refill shown in FIG. 5 around a taperedportion;

FIG. 8 is a side elevation of a regulating member employed in amodification of the ballpoint pen refill shown in FIG. 5; and

FIG. 9 is an enlarged end view taken on line IV—IV in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will be described withreference to the accompanying drawings, in which like parts aredesignated by the same reference characters.

FIGS. 1 and 2 shows a ballpoint pen refill in a first embodimentaccording to the present invention. The ballpoint pen refill has anink-accommodating tube 1 formed of a metal. The ink-accommodating tube 1has a small diameter portion 3 and a large diameter portion having adiameter that is greater than that of the small diameter portion 3. Thelarge diameter portion 2 extends rearward from the small diameterportion 3.

The small diameter portion 3 has a thin section 3 a in which a ballpointpen tip 5 is inserted, and a medium section 3 b connecting the thinsection 3 a and the large diameter portion 2. The ballpoint pen tip 5rotatably holding a ball 4 is press-fitted in a front end portion of thethin section 3 a. The ballpoint pen refill in the first embodiment has athree-section shape.

An ink 6 having a thixotropic property is filled in theink-accommodating tube 1, and a greaselike ink follower 7 is filled inthe ink-accommodating tube 1 so as to be contiguous with the rear end ofthe ink 6 having a thixotropic property. The ink follower 7 movestogether with the ink 6 as the ink 6 is consumed and prevents thereverse flow of the ink 6. An end plug 10 with a vent hole 9, whichconnects the interior of the ink-accommodating tube 1 to the exterior ofthe same, is fitted in an open rear end portion 8 of theink-accommodating tube 1.

A coil spring 12 is disposed in the ballpoint pen tip 5 so as to pressthe ball 4 closely to the inner surface of a front end portion 11 whenthe ballpoint tip refill is not in use. The rear end of the coil spring12 rests on a stepped holding portion 13 formed in the inner surface ofthe thin section 3 a of the small diameter portion 3. Although the frontend of the coil spring 12 is in direct contact with the ball 4 in thisembodiment, a pressing piece may be interposed between the ball 4 andthe coil spring 12.

The ballpoint pen refill in this embodiment is provided with aregulating member 15 having a column 15 a press-fitted in the mediumsection 3 b of the small diameter portion 3. The front end of the column15 a of the regulating member 15 is formed as an inclined end surface 14which is at a predetermined angle to a plane perpendicular to the centeraxis 0 of the ink-accommodating tube 1.

The predetermined angle of inclination of the inclined end surface 14 isdetermined taking the magnitude of centrifugal force to be exerted in adirection parallel to the center axis 0 of the ink-accommodating tube 1on the ink in a deaerating process for removing air entrapped in theink-accommodating tube 1 from the ink-accommodating tube 1 and theviscosity of the ink 6 filled in the ink-accommodating tube 1 intoconsideration so that air is not restrained from flowing by the inclinedend surface in the deaerating process.

A portion of the side surface 17 between the rear end of the inclinedend surface 14 on the front end edge 16 and the rear end of the column15 a is cut in a flat surface to form a fluid passage 18 between thecolumn 15 a and the inner surface of the medium section 3 b. The ink 6and air are able to flow through the fluid passage 18.

When the ballpoint pen refill is mounted on the rotating member of acentrifuge, not shown, with the ballpoint pen tip 5 directed radiallyoutward. The rotating member of the centrifuge is rotated to remove air,which was entrapped in the ink-accommodating tube 1 in the process offilling the ink having a thixotropic property and the greaselike ink 6follower 7 in the ink-accommodating tube 1, from the ink-accommodatingtube 1. Air staying in the ballpoint pen tip 5 flows toward the openrear end 8 as the ink 6 is moved toward the ballpoint pen tip 5 bycentrifugal force.

Air flows along the inclined end surface 14 of the regulating member 15and reaches the fluid passage 18. Further, air flows through the fluidpassage 18 into the large diameter portion 2 of the ink-accommodatingtube 1. Then, air flows through the large diameter portion 2 and escapesoutside through the open rear end 8.

When the ballpoint pen refill is impacted and the ink-accommodating tube1 and the ink 6 are forced to move relative to each other, forceresulting from the weight of the ink 6 is borne by the regulating member15.

Since the ballpoint pen refill in the first embodiment is provided withthe regulating member 15, any force resulting from the weight of the ink6 does not act on the ball 4 even if the ink-accommodating tube 1 andthe ink 6 are forced to move relative to each other by an impulsiveforce exerted on the ballpoint pen refill.

When discharging air, which was entrapped in the ink 6 in the process offilling the ink 6 having a thixotropic property and the greaselike inkfollower 7 in the ink-accommodating tube 1, through the open rear end 8of the ink-accommodating tube 1 by using the centrifuge, the flow of airstaying in front of the regulating member 15 is not obstructed by theregulating member 15. The entrapped air can surely be dischargedoutside. Therefore, the ink passage in the ballpoint pen tip 5 will notbe blocked by air remaining in the ballpoint pen tip 5 and henceunsatisfactory flow of ink will not be caused.

A ballpoint pen refill in a modification of the first embodiment will bedescribed hereinafter. FIGS. 3 and 4 show a regulating member 21employed in the ballpoint pen refill in the modification. The regulatingmember 21, similarly to the regulating member 15 of the firstembodiment, is cylindrical and has a inclined end surface. The inclinedend surface of the regulating member 21 is formed as a convex conicalsurface 22 which is projecting from the front end of the regulatingmember 21. Four grooves are formed in the side surface 23 of theregulating member 21 at equal angular intervals of 90° to form fluidpassages 24. The fluid passages 24 extend linearly between the front andthe rear end of the regulating member 21, and the ink and air are ableto flow through the fluid passages 24.

In this modification, the regulating member 21 is employed instead ofthe regulating member 15 of the first embodiment and is press-fitted inthe medium section 3 b. When the ballpoint pen refill is turned on thecentrifuge to remove air from the ink-accommodating tube 1, air stayingin the ballpoint pen tip 5 flows along the conical surface 22 and thefluid passages 24 into the large diameter portion 2 of theink-accommodating tube 1 extending behind the regulating member 21.Then, air is discharged outside through the open rear end 8 of theink-accommodating tube 1.

A ballpoint pen refill in a second embodiment according to the presentinvention will be described.

FIGS. 5 and 6 show the ballpoint pen refill in the second embodiment.The ballpoint pen refill in the second embodiment is similar inconstruction to the ballpoint pen refill in the first embodiment, exceptthat the ballpoint pen refill in the second embodiment has anink-accommodating tube 51 having a small diameter portion 53 differentin construction from that of the first embodiment, and a regulatingmember 54 different in construction from that of the first embodiment.

The small diameter portion 53 of the ink-accommodating tube 51 is of asingle-section construction different from the small diameter portion ofa two-section construction of the first embodiment.

The regulating member 54 disposed in the ink-accommodating tube 51 has acolumn 58 press-fitted in the small diameter portion 53, and a mainportion 55 extending behind the column 58. The main portion 55 has adiameter smaller than the inside diameter of a large diameter portion 52of the ink-accommodating tube 51 and greater than the diameter of thecolumn 58, and a tapered portion 56 extending between the column 58 andthe main portion 55.

The front end of the column 58 is beveled in an inclined end surface 57inclined at a predetermined angle to a plane perpendicular to the centeraxis 0 of the ink-accommodating tube 1. The angle of inclination of theinclined end surface 57 of the column 58 is determined taking themagnitude of centrifugal force to be exerted in a direction parallel tothe center axis 0 of the ink-accommodating tube 51 on an ink 6 filled inthe ink-accommodating tube 51 in a deaerating process for removing airentrapped in the ink-accommodating tube 51 from the ink-accommodatingtube 51 and the viscosity of the ink 6 filled in the ink-accommodatingtube 51 into consideration so that air is not restrained from flowing bythe inclined end surface 57 in the deaerating process.

A portion of the side surface 60 between the rear end of the inclinedend surface 57 on the front end edge 59 and a portion of the taperedportion 56 of the column 58 is linearly cut to form a fluid passage 61between the column 58 and the inner surface of the small diameterportion 53. The ink 6 and entrapped air are able to flow through thefluid passage 61.

As shown in an enlarged sectional view in FIG. 7, the ink-accommodatingtube 51 has a shoulder portion 62 provided with a recess 63. Theshoulder portion 62 extends between the large diameter portion 52 andthe small diameter portion 53. When the ink-accommodating tube 51 isinserted in a barrel, not shown, air filling the barrel is able to flowthrough the recess 63 toward an end plug 10. A projection 66 is formedin the inner surface of the shoulder portion 62 of the ink-accommodatingtube 51 at a position corresponding to the recess 63.

When the column 58 of the regulating member 54 is press-fitted in thesmall diameter portion 53, a part of the surface of the tapered portion56 comes into contact with the projection 66, so that a space 64 isformed between the inner surface of the ink-accommodating tube 51 andthe surface of the tapered portion 56.

A space extending in front of the regulating member 54 communicates witha space extending behind the regulating member 54 by means of the fluidpassage 61, the space 64 and a gap 67 between the main portion 55 of theregulating member 54 and the inner surface of the ink-accommodating tube51.

The ballpoint pen refill is mounted on the rotating member of acentrifuge, not shown, with the ballpoint pen tip 5 directed radiallyoutward. The rotating member of the centrifuge is rotated to remove air,which was entrapped in the ink-accommodating tube 51 in the process offilling the ink 6 having a thixotropic property and the greaselike inkfollower 7 in the ink-accommodating tube 51, from the ink-accommodatingtube 51. Air staying in the ballpoint pen tip 5 flows toward the openrear end 65 as the ink 6 is moved toward the ballpoint pen tip 5 bycentrifugal force.

Air flows along the inclined end surface 57 of the regulating member 54and reaches the fluid passage 61. Further, air flows through the fluidpassage 61 into the large diameter portion 52 of the ink-accommodatingtube 51. Then, the ink 6 flows through the large diameter portion 52 andescapes outside through the open rear end 65.

When the ballpoint pen refill is impacted and the ink-accommodating tube1 and the ink 6 are forced to move relative to each other, forceresulting from the weight of the ink 6 is borne by the regulating member54.

Since the ballpoint pen refill in the first embodiment is provided withthe regulating member 54, any force resulting from the weight of the ink6 does not act on the ball 4 even if the ink-accommodating tube 51 andthe ink 6 are forced to move relative to each other by an impulsiveforce exerted on the ballpoint pen refill.

When discharging air, which was entrapped in the ink 6 having athixotropic property in the process of filling the ink 6 having athixotropic property and the greaselike ink follower 7 in theink-accommodating tube 51, through the open rear end 65 of theink-accommodating tube 51 by mounting the ballpoint pen refill on therotor of a centrifuge with the ballpoint pen tip 5 directed radiallyoutward and rotating the rotor of the centrifuge to force the ink towardthe ballpoint pen tip 5 by centrifugal force, entrapped air moves towardopen rear end 65.

Air flows along the inclined end surface 57 of the regulating member 54into the fluid passage 61. Then, air flows through the space 64 and thegap 67 into the large diameter portion 52 of the ink-accommodating tube51 extending behind the regulating member 54 and is discharged outsideof the ink-accommodating tube 51 through the open rear end 65.

When the ballpoint pen refill is impacted and the ink-accommodating tube51 and the ink 6 are forced to move relative to each other, forceresulting from the weight of the ink 6 is borne by the regulating member54.

Since the ballpoint pen refill in the second embodiment is provided withthe regulating member 54, any force resulting from the weight of the ink6 does not act on the ball 4 of the ballpoint pen tip 5 even if theink-accommodating tube 51 and the ink 6 are forced to move relative toeach other by an impulsive force exerted on the ballpoint pen refill.

When air, which was entrapped in the ink 6 having a thixotropic propertyin the process of filling the ink 6 having a thixotropic property andthe greaselike ink follower 7 in the ink-accommodating tube 51, isdischarged through the open rear end 65 of the ink-accommodating tube 51by turning the ballpoint pen refill on the centrifuge, the flow of airstaying in front of the regulating member 54 is not obstructed by theregulating member 54. The entrapped air can surely be dischargedoutside. Therefore, the ink passage in the ballpoint pen tip 5 will notbe blocked by air remaining in the ballpoint pen tip 5 and henceunsatisfactory flow of ink will not be caused.

A ballpoint pen refill in a modification of the second embodiment willbe described hereinafter. FIGS. 8 and 9 show a regulating member 81employed in the ballpoint pen refill in the modification. The regulatingmember 81, similarly to the regulating member 54 of the secondembodiment, has main portion 82, a tapered portion 83 and a column 85.

The inclined end surface of the regulating member 81 in thismodification is formed as a convex conical surface 84 which extends fromthe front end of the column 85. Four grooves are formed in the sidesurface 86 of the regulating member 81 at equal angular intervals of 90°about the center axis 0 of the ink containing tube 51 aligned with thecenter axis of the regulating member 81 to form fluid passages 87. Thefluid passages 87 extend linearly between the front end of the column 85and a portion of the tapered portion 83, and the ink and air are able toflow through the fluid passages 87.

In this modification, the regulating member 81 is employed instead ofthe regulating member 54 of the second embodiment. The regulating member81 is inserted in the ink-accommodating tube 51. A space extending infront of the regulating member 81 communicates with a space extendingbehind the regulating member 81 by means of the fluid passage 87, thespace 64 and a gap 67.

When the ballpoint pen refill is turned on the centrifuge to remove airfrom the ink-accommodating tube 51, air staying in the ballpoint pen tip5 flows along the conical surface 84 and reaches the fluid passages 87.Further, air flows through the fluid passages 87, the space 64 and thegap 67 into the large diameter portion 52 of the ink-accommodating tube51 extending behind the regulating member 81. Then, air is dischargedoutside through the open rear end 65 of the ink-accommodating tube 51.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a variety of ballpoint penrefills containing an ink having a thixotropic property.

What is claimed is:
 1. A ballpoint pen refill comprising: anink-accommodating tube for containing an ink having a thixotropicproperty, said ink-accommodating tube having a small diameter portionformed at a front side of said ink-accommodating tube, and a largediameter portion formed at a rear side of said ink-accommodating tube,wherein said large diameter portion has a diameter that is greater thana diameter of said small diameter portion; a greaselike ink followerdisposed in said ink-accommodating tube, said follower being adapted tomove as the ink is consumed and to prevent a reverse flow of the ink; aballpoint pen tip inserted in a front end of the small diameter portionof said ink-accommodating tube, said ballpoint pen tip including arotatable ball; and a regulating member having a column portion that ispress-fitted in the small diameter portion of said ink-accommodatingtube, wherein the column portion of said regulating member includes afront end surface that is inclined at a predetermined angle relative toa plane that is perpendicular to an axis of said ink-accommodating tube,and substantially the entire surface of said front end surface isinclined, and wherein a fluid passage extends rearwardly from a rear endof the inclined front end surface, and along a side surface of thecolumn portion so as to allow the ink and air in said ink-accommodatingtube to flow therethrough.
 2. The ballpoint pen refill as claimed inclaim 1, wherein the predetermined angle is determined by taking intoconsideration a magnitude of a centrifugal force to be exerted in adirection that is parallel to the axis of said ink-accommodating tube onthe ink in a deaerating process for removing air entrapped in saidink-accommodating tube, and a viscosity of the ink so that the air isnot restrained from flowing by the inclined forward end surface in thedeaerating process.
 3. The ballpoint pen refill as claimed in claim 2,wherein said regulating member includes a main portion located behindthe column portion, and a tapered transitional portion connecting thecolumn portion and the main portion, wherein said main portion has adiameter that is smaller than an inside diameter of saidink-accommodating tube and greater than a diameter of the columnportion, and wherein the fluid passage extends from the rear end of theinclined front end surface through the side surface of the columnportion and beyond a rear end of the column portion.
 4. The ballpointpen refill as claimed in claim 2, wherein the inclined front end surfacecomprises a flat surface.
 5. The ballpoint pen refill as claimed inclaim 2, wherein the inclined front end surface comprises a convexconical surface projecting in a forward direction.
 6. The ballpoint penrefill as claimed in claim 1, wherein said regulating member includes amain portion located behind the column portion, and a taperedtransitional portion connecting the column portion and the main portion,wherein said main portion has a diameter that is smaller than an insidediameter of said ink-accommodating tube and greater than a diameter ofthe column portion, and wherein the fluid passage extends from the rearend of the inclined end surface through the side surface of the columnportion and beyond a rear end of the column portion.
 7. The ballpointpen refill as claimed in claim 6, wherein the inclined front end surfacecomprises a flat surface.
 8. The ballpoint pen refill as claimed inclaim 6, wherein the inclined front end surface comprises a convexconical surface projecting in a forward direction.
 9. The ballpoint penrefill as claimed in claim 1, wherein the inclined front end surfacecomprises a flat surface.
 10. The ballpoint pen refill as claimed inclaim 1, wherein the inclined surface comprises a convex conical surfaceprojecting from the front end of the column portion.
 11. The ballpointpen refill as claimed in claim 10, wherein said regulating memberincludes a plurality of fluid passages extending rearwardly from a rearend of the convex conical surface.
 12. The ballpoint pen refill asclaimed in claim 11, wherein the fluid passages are arranged in an outerperipheral surface of the column portion at equal angular intervalsabout the axis of said ink-accommodating tube.
 13. The ballpoint penrefill as claimed in claim 1, further comprising a coil spring forpressing the ball forward so as to press the ball against an innersurface of a front end of said ballpoint pen tip.
 14. The ballpoint penrefill as claimed in claim 1, wherein the small diameter portion of saidink-accommodating tube has a reduced diameter section in which saidballpoint pen tip is inserted, a medium section having a diameter thatis greater than a diameter of the reduced diameter section and smallerthan the diameter of the large diameter portion, said medium sectionconnecting the reduced diameter section and the large diameter portion,and the column portion of said regulating member is press-fitted in themedium section of the small diameter portion.
 15. The ballpoint penrefill as claimed in claim 1, further comprising an end plug fitted inan open rear end of said ink-accommodating tube, wherein said plug has avent hole.
 16. A ballpoint pen refill comprising: an ink-accommodatingtube containing ink having a thixotropic property, saidink-accommodating tube having a small diameter portion formed at a frontside of said ink-accommodating tube, and a large diameter portion formedat a rear side of said ink-accommodating tube, wherein said largediameter portion has a diameter that is greater than a diameter of saidsmall diameter portion; a greaselike ink follower disposed in saidink-accommodating tube, wherein said follower is adapted to move as theink is consumed and to prevent a reverse flow of the ink; a ballpointpen tip inserted in a front end of said small diameter portion of saidink-accommodating tube, said ballpoint pen tip including a rotatableball; and a regulating member having a column portion that ispress-fitted in said small diameter portion, a main portion locatedbehind the column portion, and a tapered transitional portion connectingthe column portion and the main portion, wherein a front end surface ofthe column portion is inclined at a predetermined angle relative to aplane that is perpendicular to an axis of said ink-accommodating tube,wherein the main portion of said regulating member has a diameter thatis less than an inside diameter of said ink-accommodating tube andgreater than a diameter of the column portion of said regulating member,wherein the tapered transitional portion is positioned in saidink-accommodating tube so as to not be in close contact with an innersurface of said ink-accommodating tube, and wherein a fluid passageextends rearwardly from a rear end of the inclined front end surface,along a side surface of the column portion to at least a portion of thetapered transitional portion in order to allow the ink and any air insaid ink-accommodating tube to flow through the fluid passage.
 17. Theballpoint pen refill as claimed in claim 16, wherein saidink-accommodating tube comprises: a shoulder portion forming atransitional portion between the small diameter portion and the largediameter portion; a recess formed on an outside surface of the shoulderportion; a projection formed on the inner surface of saidink-accommodating tube at a position corresponding to the recess,wherein the tapered transitional portion contacts the projection so thata space is formed between the inner surface of said ink-accommodatingtube and a surface of the tapered transitional portion.
 18. Theballpoint pen refill as claimed in claim 17, wherein the inclined frontend surface of the column portion comprises a flat surface.
 19. Theballpoint pen refill as claimed in claim 16, wherein the inclined frontend surface of the column portion comprises a flat surface.
 20. Theballpoint pen refill as claimed in claim 16, wherein the inclined frontend surface of the column portion comprises a convex conical surfacethat projects in a forward direction.